ARMMS Conference addresses efficiency of microwave systems

Sapphire CMOS technology, SMT packaging of microwave ICs and envelope tracking techniques were just some of the highlights of the November ARMMS conference, which was held near Cambridge, UK, on 19 and 20 November. John Crute, Chairman of the RF & Microwave Society, welcomed over 70 delegates, especially those who travelled from Germany and the USA. He pointed out the fact that the organisation had reached 30 years of age, was in good shape and had steadily increased in size.

The conference culminated in the presentation of the Steve Evans-Pughe Best Paper Award, which went to Ian Greenshields for his explanation of Peregrine Semiconductor’s Silicon on Sapphire CMOS technology. He showed how the very low loss characteristics of sapphire allows dynamic tuning of mobile phone antennas so achieving a 3 dB improvement in performance and doubling battery life. The necessary control circuits are easily integrated as they are fabricated using the same CMOS technology.

On the subject of SMT packaging of microwave ICs, Liam Devlin from Plextek considered the operation of the standard QFN package to frequencies over 20 GHz when mounted on Rogers 4003 PCB material. The importance of source (or earthing) inductance for good stability was emphasised. Below is a video of his presentation at the conference.

The phrase ‘data scrapes’ was coined by Gerard Wimpenny of Nujira. Careful characterisation of the RF PA is the key to high efficiency when applying the envelope tracking (ET) technique. It was noted that ET is more stable with load changes than a conventional amplifier.

Methods of improving power amplifier (PA) performance using the active load pull technique, were explored by Dominic FitzPatrick of PoweRFul Microwave. He showed how the method is applied to the second and third harmonic terminations allowing ‘waveform engineering’ of the RF voltages and better efficiency with octave bandwidths.

Stability, in multi-stage amplifiers, was addressed by Malcolm Edwards of Applied Wave Research. He explained the use of the STAN software tool from AMCAD Engineering, which automatically identifies the poles and zeros in a complex network and so predicts stability. He also referred to ‘noise bumps’ (also known as noisy precursors) as the first sign of chaotic behaviour.

As well as the conference, an exhibition supported by seventeen companies proved to be a great place to meet and network and, as always, the RF & Microwave Society dinner provided a further networking opportunity and proved to be a very sociable occasion. The next conference ARMMS conference will be in Oxford, UK on 22 and 23 April 2013.